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Question: Answered & Verified by Expert
The function $f: R \rightarrow R$ defined by $f(x)=(x-1)(x-2)(x-3)$ is
MathematicsFunctionsJEE Main
Options:
  • A One-one but not onto
  • B Onto but not one-one
  • C Both one-one and onto
  • D Neither one-one nor onto
Solution:
1003 Upvotes Verified Answer
The correct answer is: Onto but not one-one
We have $f(x)=(x-1)(x-2)(x-3)$
and $f(1)=f(2)=f(3)=0 \Rightarrow f(x)$ is not one-one.
For each $y \in R$, there exists $x \in R$ such that $f(x)=y$. Therefore $f$ is onto. Hence $f: R \rightarrow R$ is onto but not one-one.

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